1. Field of the Invention
The present disclosure relates generally to an improved cementing plug system with a subsea plug launching tool for offshore oil and gas wells. More particularly, the present disclosure is directed to an improved subsea cementing plug system well suited for cementing subsea casing strings in deep water.
2. Description of the Related Art
Offshore drilling activity continues to move into deeper water with depths of up to 10,000 feet now being experienced. Subsea launch cementing plug technology was developed to address the shallow water depths of 500 feet or less. Operational challenges such as non-observance of plug launch pressures, free fall rate of weighted ball, and inability to wipe drill pipe inside diameter prior to cementing have been experienced moving into deeper waters. Due to operations in deeper water, it can take a long time for an operator to get a pressure indication that the ball has release the bottom cement plug potentially causing the operator to start pumping displacement fluid and cement prematurely. In this instance there is no pressure indication when the bottom plug has launched because the ball is being pumped down.
Prior cementing systems have utilized shear pins to selectively secure the cement plugs to the launching tool. However, the use of shear pins potentially permits the cement plugs to be launched by any differential pressure which exerts a force across the shear pins potentially inadvertent launching of the cement plug. The use of shear pins also potentially permits the wrong plug to be launched due to a pressure differential. It would be beneficial to provide a system that prevents inadvertent launching of a cement plug.
In light of the foregoing, it would be desirable to provide a subsea cement plug system that uses a top plug and a bottom plug that seals at the bottom of the bottom plug after the cement has been displaced into the casing annulus and the top plug has been bumped. It would also be desirable to provide a subsea cement system that connects the top plug to a bottom plug with a collet to prevent the premature separation of the plugs. It would further be desirable to provide a subsea cement system that used full bore cement plugs that allow a device, such as a ball, to be dropped through the plugs that may be used to actuate a tool located below the cement plugs, such as an auto fill float collar.
The present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.